Starting to build my library, and ROM size hasn’t been an issue now until I got to PS1.
The file sizes aren’t MASSIVE, but it’s a little annoying to download each individual .CUE/.BIN, and convert to .CHDs.
I looked at some torrents, but they’re mostly a mishmash of formats and clearly put together by someone that is not well organized.
Vimms lair is a good choice, though i don’t think they’re in .chd by default, rather just .iso, or a compressed .iso format. It’s highly consistent in naming conventions, and has a pretty damn near full collection. Main downside is limited downloading speed, and no concurrent downloads, but if you’re just looking to download games you’re interested in and not every ps1 game, it should be fine